The present invention relates to photolithography systems and methods, specifically, to maskless photolithography devices and methods for creating 2-D and 3-D patterns using a plasma display.
Photolithography systems are known in the art that direct light beams onto a photosensitive surface covered by a mask, etching a desired pattern on the substrate corresponding to the void areas of the mask. Maskless photolithography systems are also known in the art as described in Singh-Gasson, Sangeet et al., Nature Biotechnology 17, 974-78, 1999. The system described in that article uses an off-axis light source coupled with a digital mirror device to fabricate DNA chips containing probes for genes or other solid phase combinatorial chemistry to be performed in high-density microarrays.
A number of patents also exist which relate to maskless photolithography systems, including U.S. Pat. Nos. 5,870,176; 6,060,224; 6,177,980; and 6,251,550; all of which are incorporated herein by reference.
Plasma displays, as known in the art, generally consist of two glass plates, each containing a network of parallel electrodes and intersecting address electrodes, sealed to form a discharge envelope filled with a neon and xenon gas mixture. A gas discharge plasma is created by applying an electric field between the electrodes. The plasma generates ultraviolet light, which in turn excites a phosphor coating inside the glass envelope to generate a pixel of light.
A number of patents directed to plasma display devices exist, including U.S. Pat. Nos. 6,376,986, 6,362,799, 6,344,715, and 5,661,500; all of which are incorporated herein by reference.
While the previously described maskless photolithography systems address several of the problems associated with mask based photolithography systems, such as distortion and uniformity of images, problems still arise. Notably, maskless photolithography systems are complex and require complex optical systems and micromirror arrays.
Typically, maskless photolithography systems require two sets of complex optics: one set of optics to condition light emanating from a light source and directed to a spatial light modulator and a second set of optics to further conditions and direct the light reflected from the spatial light modulator. Consequently, two sets of complex optics and a light source must be mechanically aligned and maintained for a maskless system. For the digital mirror device, digital shifting of a mask pattern has been proposed to resolve micromirror to object alignment, this technique cannot be used to align the light source in relation to the micromirror array.
In addition, the use of micromirror arrays in maskless photolithography systems poses other problems. Micromirror arrays are specialized, custom devices that require complex driving circuitry and are subject to a phenomenon known as xe2x80x9cstiction.xe2x80x9d Stiction occurs when the individual mirrors in a micromirror array xe2x80x9cstickxe2x80x9d in a specific orientation if left in that position for an extended period. Consequently, a higher voltage needs to be applied to the mirror drive to point the mirror in another desired direction. Thus, the micromirror array consumes more power than normal and the reliability of the mirror can be affected.
Accordingly, there is a need in the art for a method and system for maskless photolithography to eliminate unnecessary complexity and provide a direct radiation means to provide a more effective way to fabricate custom devices. This system needs to eliminate redundant optical fixtures required by micromirror array based maskless photolithography systems that rely on reflection of light generated by a separated light source. The system needs to provide a single device for generating patterned light and directing the patterned light to an object, thereby eliminating the need for a separate light source and associated optics. In addition, the system needs to combine ease of use, reconfigurability, and the ability to provide coarse manual alignment and automated fine alignment of mask patterns. In summary, the system needs to combine all the advantages of a maskless photolithography system with the advantages of pixel addressable, UV emitting plasma display to eliminate complexity and provide a simpler, more cost effective maskless photography system.
In view of the foregoing deficiencies of the prior art, it is an object of the present invention to provide a maskless photolithography system using a plasma display for creating patterns on objects.
It is another object of the present invention to provide a method of maskless photolithography that uses a plasma display device to generate and direct patterned light on an object.
It is still another object of the present invention to provide a plasma device display that lacks phosphor coatings, whereby the plasma device generates ultraviolet (UV) light directly.
It is still another object of the present invention to provide a positioning fixture; selectively movable in a three dimensions to accurately position a substrate for maskless photolithography using a plasma device as a source of patterned light.
It is another object of the present invention to provide plasma based, maskless photolithography system for creating micro and macro three-dimensional structures.
To achieve these objects, a system and method are provided to create two dimensional and three dimensional structures using a maskless photolithography system that is directly reconfigurable and does not require masks, templates or stencils to create each of the planes or layers on a multi layer two-dimensional or three dimensional structure. In an embodiment, the invention uses a plasma display device comprising ultraviolet (UV) light emitting pixels to illuminate a substrate that has photoreactive compounds applied to the exposed surface. The plasma display comprises an array of miniature plasma discharge cells, or pixels, that combine light generation and modulation to create individually addressable UV light pixels. Each element of an array of UV light pixels in a plasma display is activated by a network of electrodes and can be selectively turned on and off to create a desired two-dimensional light pattern. The emitted light beam, comprising light from each individual UV light pixel, can be directed towards a target substrate coated with a photoreactive compound. The UV light reacts with the photoreactive compound to create a pattern on the substrate corresponding to the illumination pattern.
The desired pattern is designed and stored using conventional computer aided drawing techniques and is used to control the xe2x80x9cfiringxe2x80x9d of the individual pixels of the plasma display to create the corresponding desired mask pattern.
In addition, an alignment fixture, movable in three dimensions, for mounting of the substrate is provided. The alignment fixture allows the affixed substrate to be moved in three dimensions, providing alignment in two, coplanar dimensions and a third dimension perpendicular to the two coplanar dimensions. By providing alignment in the third dimensional direction, the invention advantageously provides the capability to produce three-dimensional structures on a substrate.
The advantages of the invention are numerous. One significant advantage is that the tasks of light generation and patterning in a maskless photolithography system can be combined into a single plasma display device. Thus, need for a separate light source and optics stage as in conventional micromirror array-based systems is eliminated, resulting in a simpler, more cost efficient system. Another advantage is that a plasma display device is inherently more reliable than a micromirror device. Yet another advantage is that plasma devices are readily available as off-the-shelf devices, complete with readily adaptable control electronics.
Still another advantage is the ability to use the invention as a reconfigurable, rapid prototyping tool for creating two-dimensional and three-dimensional micro and macroscopic objects. Yet another advantage of the invention is that it provides the ability to reduce prototyping costs and enable devices to be fabricated more quickly with less risk. Still another advantage of the current invention is a reduction in cost for prototyping activities realized by the elimination of physical masks. Yet another advantage of the current invention is that pattern generation can be performed optically without having to use expensive vacuum system required by conventional mask-based photolithography. A particular advantage of the current invention is the ability to create three-dimensional devices using an alignment stage to selectively expose successive layers in a substrate.
As a result, any arbitrary micro or macroscopic structure can easily and quickly be created in substrates such as polymers, metals, or ceramics. Patterns such as microfluidic networks, thin film devices, hybrid material devices, micro electromechanical machines (MEMs), and combinations of the above mentioned devices can be created using the reconfigurable, application specific photolithography system disclosed. In addition, because plasma arrays are available in large formats, large-scale objects can be patterned in one exposure, obviating the need to sequentially expose smaller areas until the entire surface is exposed.
All patents, patent applications, provisional applications, and publications referred to or cited herein, or from which a claim for benefit of priority has been made, are incorporated herein by reference in their entirety to the extent they are not inconsistent with the explicit teachings of this specification.
Other aspects and advantages of the invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings, illustrating, by way of example, the principles of the invention.